Variability in the fraction of ambient fine particulate matter found indoors and observed heterogeneity in health effect estimates

Hodas, Nathan O.; Meng, Qingyu; Lunden, Melissa M.; Rich, David Q.; Özkaynak, Halûk; Baxter, Lisa; Zhang, Qi; Turpin, Barbara J.

doi:10.1038/jes.2012.34

Cited by 50 publications

(28 citation statements)

References 49 publications

(58 reference statements)

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“…Because Americans spend nearly 90% of their time indoors and almost 70% of their time at home, on average (Klepeis et al 2001), and outdoor particles infiltrate and persist in buildings with widely varying efficiencies (Thatcher and Layton 1995;Thatcher et al 2003;Williams et al 2003;Rim et al 2010;Chen and Zhao 2011;Stephens and Siegel 2012), much of human exposure to particulate matter of outdoor origin actually occurs indoors, particularly inside residences (Meng et al 2005;Wallace and Ott 2011;Hodas et al 2012Hodas et al , 2013MacNeill et al 2012MacNeill et al , 2014Baxter et al 2013). …”

Section: Introductionmentioning

confidence: 97%

Modeling the impact of residential HVAC filtration on indoor particles of outdoor origin (RP-1691)

Azimi

Zhao

Stephens

2016

Science and Technology for the Built Environment

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Much of human exposure to airborne particles of outdoor origin, including fine particles smaller than 2.5 μm (PM 2.5 ) and ultrafine particles smaller than 0.1 μm (UFPs), occurs in residences. High-efficiency central HVAC filters are increasingly being used in residences, but questions remain about their effectiveness in reducing indoor PM 2.5 and UFPs of outdoor origin in homes operating under realistic conditions (e.g., with HVAC systems operating only to meet heating or cooling demands). Here dynamic building energy and indoor air mass balance modeling are combined to estimate the impacts of 11 HVAC filters (minimum efficiency reporting value [MERV] 5 through high-efficiency particulate air [HEPA]) on indoor concentrations of PM 2.5 and UFPs of outdoor origin in multiple vintages of prototypical single-family residences relying on either infiltration or mechanical ventilation systems in 22 U.S. cities. Results demonstrate that higher-efficiency HVAC filters can meaningfully reduce indoor proportions of outdoor PM 2.5 and UFPs inside residences, but home vintage, climate zone, and ventilation strategy strongly influence the outcomes due to widely varying air exchange rates, HVAC system runtimes, and sources of ventilation air. Higher efficiency filters had a greater impact in older, leakier homes relying on infiltration alone and in new homes relying on supply-only mechanical ventilation systems designed to meet ASHRAE Standard 62.2.

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Section: Introductionmentioning

confidence: 97%

Modeling the impact of residential HVAC filtration on indoor particles of outdoor origin (RP-1691)

Azimi

Zhao

Stephens

2016

Science and Technology for the Built Environment

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“…Because speciation measurements were not available for all central-site-monitor locations, values for the New Brunswick monitoring station, which were most highly correlated with data from other monitors across the state, were used. For details, see Hodas et al 20 and Baxter et al 21 . With this approach, particle losses indoors varied daily with variations in PM 2.5 composition.…”

Section: Methodsmentioning

confidence: 99%

“…We concluded that exposure misclassification due to variability in F could partially explain this observed geographic heterogeneity in ambient-PM-mediated health effect estimates. 20 …”

Section: Introductionmentioning

confidence: 99%

Refined ambient PM2.5 exposure surrogates and the risk of myocardial infarction

Hodas

Turpin

Lunden

et al. 2013

J Expo Sci Environ Epidemiol

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Using a case-crossover study design and conditional logistic regression, we compared the relative odds of transmural (full-wall) myocardial infarction (MI) calculated using exposure surrogates that account for human activity patterns and the indoor transport of ambient PM2.5 with those calculated using central-site PM2.5 concentrations to estimate exposure to PM2.5 of outdoor origin (exposure to ambient PM2.5). Because variability in human activity and indoor PM2.5 transport contributes exposure error in epidemiologic analyses when central-site concentrations are used as exposure surrogates, we refer to surrogates that account for this variability as “refined” surrogates. As an alternative analysis, we evaluated whether the relative odds of transmural MI associated with increases in ambient PM2.5 is modified by residential air exchange rate (AER), a variable that influences the fraction of ambient PM2.5 that penetrates and persists indoors. Use of refined exposure surrogates did not result in larger health effect estimates (ORs = 1.10 – 1.11 with each interquartile range increase.), narrower confidence intervals, or better model fits compared to the analysis that used central-site PM2.5. We did observe evidence for heterogeneity in the relative odds of transmural MI with residential AER (effect-modification), with residents of homes with higher AERs having larger ORs than homes in lower AER tertiles. For the level of exposure-estimate refinement considered here, our findings add support to the use of central-site PM2.5 concentrations for epidemiological studies that employ similar case-crossover study designs. In such designs, each subject serves as his or her own matched control. Thus, exposure error related to factors that vary spatially or across subjects should only minimally impact effect estimates. These findings also illustrate that variability in factors that influence the fraction of ambient PM2.5 in indoor air (e.g., AER) could possibly bias health effects estimates in study designs for which a spatio-temporal comparison of exposure effects across subjects is conducted.

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“…pollutant-specific residential infiltration rates, and time spent on or near roadways) may also be effect modifiers in epidemiological studies of both local and regional pollutants (26, 30, 34-36). As epidemiological studies begin to focus more on PM 2.5 components, relevant residential infiltration models must be developed to account for component specific penetration efficiencies and decay rates.…”

Section: Recommendations For Future Workmentioning

confidence: 99%

Exposure prediction approaches used in air pollution epidemiology studies: Key findings and future recommendations

Baxter

Dionisio

Burke

et al. 2013

J Expo Sci Environ Epidemiol

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Many epidemiologic studies of the health effects of exposure to ambient air pollution use measurements from central-site monitors as their exposure estimate. However, measurements from central-site monitors may lack the spatial and temporal resolution required to capture exposure variability in a study population, thus resulting in exposure error and biased estimates. Articles in this dedicated issue examine various approaches to predict or assign exposures to ambient pollutants. These methods include: combining existing central-site pollution measurements with local- and/or regional-scale air quality models to create new or “hybrid” models for pollutant exposure estimates, and using exposure models to account for factors such as infiltration of pollutants indoors and human activity patterns. Key findings from these articles are summarized to provide lessons learned and recommendations for additional research on improving exposure estimation approaches for future epidemiological studies. In summary, when compared to use of central-site monitoring data, the enhanced spatial resolution of air quality or exposure models can have an impact on resultant health effect estimates, especially for pollutants derived from local sources such as traffic (e.g. EC, CO, and NOx). In addition, the optimal exposure estimation approach also depends upon the epidemiological study design. We recommend that future research develop pollutant-specific infiltration data (including for PM species), and improve existing data on human time-activity patterns, and exposure to local source (e.g. traffic), in order to enhance human exposure modeling estimates. We also recommend comparing how various approaches to exposure estimation characterize relationships between multiple pollutants in time and space, and investigating the impact of improved exposure estimates in chronic health studies.

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Variability in the fraction of ambient fine particulate matter found indoors and observed heterogeneity in health effect estimates

Cited by 50 publications

References 49 publications

Modeling the impact of residential HVAC filtration on indoor particles of outdoor origin (RP-1691)

Modeling the impact of residential HVAC filtration on indoor particles of outdoor origin (RP-1691)

Refined ambient PM2.5 exposure surrogates and the risk of myocardial infarction

Exposure prediction approaches used in air pollution epidemiology studies: Key findings and future recommendations

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